• Home
• About
• Tools
• Experiments
• Systems
• Contact

Brown Soft Scale

DESCRIPTION Adults: Living adult female brown soft scales are pale yellowish green to yellowish brown, often mottled with brown spots. Older females are brown. The body is usually oval in outline, 2.5 to 4 millimeters in length and slightly convex in profile. The shape tends to vary according to position on the host plant. Males look like tiny two-winged wasps or flies and are rare.

Other Stages: Crawlers and young nymphs are yellow and almost flat in profile. Parasitized nymphs are dark brown to black and convex. Crawlers have well-developed legs and antennae and are quite active until settling. Older nymphs are sessile. BIOLOGY Host Plants: Brown soft scale has been reported feeding on hundreds of different plants. It can survive on most greenhouse plants, but seems to prefer perennials over annuals. Ferns are a favored host.

Damage: Brown soft scale is probably the most frequently encountered scale on plants indoors. Infestations of brown soft scale can become so heavy as to encrust the stems and petioles of their host plant. They also settle on leaves, usually along midribs and occasionally on the fruit. Large colonies remove large quantities of plant fluids and can cause wilting, but they seldom kill their host. Immatures and adults produce much honey dew that serves as a medium for the growth of sooty molds. These fungi inhibit photosynthesis and make infested plants unsightly. Other insects such as ants and wasps are attracted to feed on the honeydew.

Life Cycle: Females are ovoviviparous and retain the eggs in the body until hatching. Brown soft scales are born as active crawlers but remain under the body of the female for a short time before emerging and selecting a feeding site to settle and complete their development. Females molt twice before reaching maturity. Males undergo four molts before emerging as winged adults, but are rarely seen. All stages are found throughout the year in warmer regions and in greenhouses. Brown soft scales can complete three to seven generations per year depending on temperature. It takes about 60 days to complete a generation.

MANAGEMENT STRATEGIES Brown soft scales are surprisingly difficult to control even though there is an external egg stage and only a few very young nymphs are protected by the body of the mother.

Biological Control: Although reported as a pest species of many host plants in many countries, outdoors it may be suppressed by natural enemies in many areas. Scutellista cyanea Motschulsky is a common parasite and Metaphycus luteolus Timberlake controls brown soft scale in California. The lady beetle Ryzobius lophanthae is a soft scale predator.

Pesticides: For specific chemical control recommendations, consult the Cooperative Extension Service.

Broad Mite

DESCRIPTION Adults: Broad mites are almost microscopic (less than 0.2 millimeter long). They are translucent and colorless to pale brown. There are four pairs of legs; the last pair in the female ends in a long hair; the last pair on the male ends in a strong claw.

Eggs: The egg is elliptical, translucent, colorless, about 0.08 millimeter long, and is covered by 29 to 37 whitish bumps.

Larvae: The young broad mite has three pairs of legs and is whitish due to minute ridges on the skin. It is about 0.1 millimeter long. BIOLOGY Host Plants: Broad mites infest African violet, ageratum, azalea, begonia, dahlia, gerbera, gloxinia, ivy, jasmine, impatiens, lantana, marigold, peperomia, snapdragon, verbena, and zinnia.

Damage: Infested plants become unthrifty. Leaves curl downward and turn coppery or purplish. Internodes shorten and lateral buds break more than normal. This new growth may also be stunted or killed, which forces out additional shoots. Flowers are distorted and fail to open normally. Unless controlled, broad mites usually destroy the commercial value of infested ornamental corps. Broad mites damage flowers and foliage of begonia and cyclamen, and bronze the lower leaf surfaces. Broad mites are so small that they are virtually invisible on the host plant even with a good hand lens.

Life Cycle: Female broad mites lay 30 to 76 eggs on the leaf surface over an 8- to 13-day oviposition period. Unmated females lay male eggs; mated females usually lay four female eggs for every male egg. The larvae hatch in 2 or 3 days and emerge from the egg shell to feed. Larvae are slow moving and do not disperse far. In 2 or 3 days, the larvae develop into a quiescent larval stage. Quiescent female larvae become attractive to the males which pick them up and carry them to the new foliage. Males and females are very active, but the males apparently account for much of the dispersal of a broad mite population in their frenzy to carry the quiescent female larvae to new leaves. When females emerge from the quiescent stage, males immediately mate with them. Males live 5 to 9 days; females live 8 to 13 days.

MANAGEMENT STRATEGIES Cultural control: Broad mites are very sensitive to heat. Lowering infested plants into water held at 43 to 49°C for 15 minutes will destroy broad mites without damaging the plants.

Pesticides: Broad mites are susceptible to various miticides. However, they are more difficult to control in winter than in summer due to lower greenhouse temperatures. For specific chemical control recommendations, consult the Cooperative Extension Service.

Root Mealybug

DESCRIPTION Adult Females: The ground mealybug is white and 2.4 to 3.9 millimeters long. It resembles a springtail, but moves much more slowly and cannot jump. The ground mealybug has slender waxy filaments that form a sort of netting over some individuals. The ground mealybug also secretes a small amount of wax, which can give the soil a somewhat bluish appearance when the mealybugs are abundant. Pritchard’s mealybug is snow white and 1.6 to 2.1 millimeters long and oval. It has small to non-existent eyes.

BIOLOGY Host Plants: The ground mealybug feeds on the roots of anemone, chrysanthemum, gladiolus, iris, and numerous other flowers, shrubs, and ornamental grasses. Pritchard’s mealybug has become a serious pest of African violet, although it also infests Achillea, Arctostaphylos, Geum, and Polygala.

Damage: At times the ground mealybug becomes abundant enough to damage its host. Pritchard’s mealybug causes devitalization, foliage deterioration, and even death of its host plant.

Life Cycle: Little has been published on the life history of root mealybugs. When infested African violets are irrigated, Pritchard’s mealybugs crawl out of the drainage holes and spread throughout the greenhouse. Eggs are laid in a loose ovisac in clusters of at least six eggs. All stages can be found on the roots and potting mix of African violets where they resemble slow moving, snowy white collembola.

MANAGEMENT STRATEGIES
Pesticides: Pesticides applied as dips, drenches, or granules are more effective for root mealybug control than are foliar sprays. For specific chemical control recommendations, consult the Cooperative Extension Service.

Biosduval scale

DESCRIPTION Adult Females: Cover of the adult female boisduval scale is circular or oval, thin, flat, white to light yellow, semitransparent, and 1.2 to 2.25 millimeters in diameter. Exuviae central to subcentral in position.

Other Stages: The male cover is somewhat rectangular in shape, elongate, about 1 millimeter in length, and snow white with three ridges down the back.

Eggs: Boisduval scale eggs are oval and pale yellow to pale orange.

Nymphs: Newly settled nymphs are pale orange. BIOLOGY Host Plants: Cattleya and Cymbidium orchids are the most common hosts, but this scale insect thrives on the leaves and bark of other orchids, palms, banana, and cacti.

Damage: New growth is frequently attacked prior to opening, and leaves may be killed if the infestation is dense. Lighter infestations produce irregular chlorotic spots that mark feeding sites and spoil the appearance of the leaves.

Life Cycle: Under greenhouse conditions, boisduval scale can complete its life cycle in about 50 days. Females may produce up to 200 eggs in a lifetime.

Eggs: Eggs hatch in 5 to 7 days and most of the crawlers settle to feed within 24 hours after hatching. The first stage lasts about 10 days, the second about 8 to 10 days for females and 15 for males. After mating, females retain their eggs for a short period, then oviposit. Because females produce eggs over a long period, generations overlap, and usually all stages can be found at any one time. Crawlers can settle anywhere on the leaf, but seem to prefer the midrib and major veins.

MANAGEMENT STRATEGIES Try to purchase plants from a supplier who does not have a scale infestation.

Pesticides: When scales are encountered, horticultural oils give adequate control without excessive phytotoxicity. Two thorough treatments 2 weeks apart should give good control. Boisduval scale crawlers often establish themselves near the base of the plant and in leaf sheaths making control difficult. Also, both upper and lower leaf surfaces are attacked, so thorough coverage of any treatment is essential. For specific control recommendations, consult the Cooperative Extension Service.

Shore Fly

DESCRIPTION Adults: Shore flies in the genus Scatella are small (2 millimeters), black flies with reddish eyes and gray wings with clear spots. Shore flies resemble eye gnats, fruit flies, or vinegar flies in general shape. Shore flies are sometimes confused with darkwinged fungus gnats which are about the same size and color. (Darkwinged fungus gnats are shaped more like miniature mosquitoes and have relatively long legs and antennae.)

Eggs: Shore fly eggs are about 0.42 long and 0.2 millimeter wide. They are fairly rounded at both ends although there are small lobes on one end. The surface of the egg is covered with minute, faint polygons. The eggs remain white throughout the development of the embryo.

Larvae: The tiny first stage maggots have two spiracles only at the rear. The next two larval stages have two spiracles on the rear and a spiracle on either side near the head. The mature maggot is about 2.6 millimeters long and 0.9 millimeter wide and 0.5 millimeter high. The hind spiracles are black and are located at the end of small but conspicuous tubes. The anterior spiracles each resemble the fingers of a slightly inflated rubber glove but these spiracles are microscopic and inconspicuous.

Puparium: The puparia of Scatella shore flies are brown to dark brown, curved, and tapered on both ends. The puparia are about 2.6 millimeters long and 0.9 millimeter wide. At the hind end, the spiracles resemble stiff antennae. On the front, the anterior spiracles stick out sideways like microscopic horns. The puparia are curved toward the top side of the developing fly.

BIOLOGY Host Plants: Adult and immature shore flies feed on microscopic algae, dinoflagellates, bacteria, cyanobacteria, and other unicellular forms.

Damage: Neither adult nor immature shore flies feed upon ornamental plants. The damage caused by shore flies consists primarily in the excrement (“fly specks”) left on the foliage of bedding plants and other ornamentals.

Because shore flies are often confused with darkwinged fungus gnats, control efforts are often wasted (darkwinged fungus gnats may be harmful to plants but are relatively easy to control; shore flies are harmless but are very difficult to control with insecticides). Sometimes shore flies become so abundant in greenhouses that the sheer numbers of flies becomes a deterrent to customers browsing or even employees working.

Life Cycle: Scatella shore flies are commonly found in greenhouses where they breed in algae growing on the potting mix, pots, benches and floors.

Females scatter eggs right on the surface of the potting mix. The eggs hatch in 2 to 3 days. The larvae are found within the crust of algae and very top layer of potting mix. The maggots feed on bacteria and yeasts as well as diatoms and flagellates growing on the surface of the potting mix.

The larvae mature in 3 to 6 days and pupate inside the skin of the last larval stage (this kind of pupa is called a puparium). The last larval skin affords the relatively tender and completely helpless pupa protection from environmental hazards (including insecticides). Some of the puparia are found on top of the potting mix or are very close to the surface. A new generation of adult flies emerges 4 to 5 days later. The adults crawl about on the surface of the potting mix, on the plants or they fly about the pots and plants. The flies move and fly rapidly but generally stay close to their breeding sites. The adults feed primarily on diatoms and flagellates on the surface of the potting mix or mats.

MANAGEMENT STRATEGIES Cultural Controls: Cultural methods of shore fly management include avoiding excessive use of water during irrigation, using the minimal optimum levels of fertilizers for adequate plant growth (and lower levels of excess fertilizers that encourage algal blooms), and a drier greenhouse environment. Algae on mats, benches, the walls or other structural members, and the soil beneath benches should be eliminated by using an approved algaecide. Because shore fly maggots can also develop on rotting vegetable matter, general greenhouse sanitation should also help suppress shore fly numbers.

Pesticides: Perhaps because of the high biological activity of the surface of the potting mix, the protection afforded the pupa by the last larval skin, and the water repellent property of the adults, insecticides do not seem to readily suppress shore flies in greenhouses.

Banded Greenhouse Thrips

DESCRIPTION Adults: Female banded greenhouse thrips, approximately 1.5 mm long, are primarily yellow at first but gradually darken to brown or black. The eyes are red; the narrow, fringed wings are gray brown with 3 white crossbands. Males are rare.

Eggs: When first deposited, the translucent elongate eggs are white 0.25 mm in length. Before hatching, each eggs wells and becomes dull white.

Larvae: The yellow or white larvae vary from 0.48 to 1.5 mm in length. They are wingless and have red eyes.

Pupae and Prepupae: These stages are white and found on the leaves. There are usually more individuals on the lower surface. BIOLOGY Distribution: Although sporadically distributed through out North America, banded greenhouse thrips are widely distributed throughout the world. They are particularly common in the British Isles, Europe, and East Africa.

Host Plants: In the greenhouse, banded greenhouse thrips attack many crops including cucumbers, begonias, cacti, date palm, bananas, callas, cestrum, amaryllis, aralia, chrysanthemum, dracaena, rubber tree, gardenia, croton, hydrangea, moon flower, schefflera, screw pine, tomato, and Mexican tea. In one experiment in Georgia, 44 species of plants were used as host plants out of 50 presented. The banded green house thrips showed definite preference for some species among those accepted as host plants.

Damage: Banded greenhouse thrips pierce plant tissues with their mouthparts and suck the juices. As a result, irregular white spots form on the leaf giving it an overall silver appearance. Eventually, these areas dry out and turn light brown. Some defoliation results.

Life Cycle: The banded greenhouse thrips, sometimes referred to as the sugar beet thrips, has gained notoriety as a major floricultural pest. In North Carolina, this thrips was first reported as a greenhouse pest in 1943 on white callas. In the greenhouse, thrips may breed continuously and have several generations per year. Eggs are deposited on the underside of leaves or along the stem. Approximately 2 weeks later, larvae emerge and begin feeding. Colonies of young larvae congregate on the underside of leaves and individuals are often covered with a watery globule of excrement. As the larvae feed, they develop through four instars, molting between each stage. The more mature larvae are typically found along leaf midribs or among dried-up foliage. After a larval stage of approximately 18 days, banded greenhouse thrips pupate. Adult thrips that emerge shortly thereafter are less voracious feeders than the larvae. Adults live 40 or more days and females may reproduce with or without mating. Males of this species are rarely found.

CONTROL: Banded greenhouse thrips are vulnerable to contact insecticides. Stored bulbs can be dusted with such an insecticide to prevent a thrips infestation on plants the following season.

Silverleaf Whitefly

DESCRIPTION Adults: The silverleaf whitefly is slightly smaller (about 0.96 mm in the female and 0.82 mm in the male) and slightly yellower than most other whitefly pests of flowers. The head is broad at the antennae and narrow towards the mouth parts. The wings are held roof-like at about a 45° angle, whereas other whiteflies usually hold the wings nearly flat over the body. Hence, the silverleaf whitefly appears more slender than other common whiteflies.

Eggs: The eggs are inserted on end in the undersides of new leaves. The eggs are whitish to light beige with the apex tending to be slightly darker.

Nymphs: The nymphal stages appear glassy to opaque yellowish and may or may not have dorsal spines, depending on leaf characteristics. The body is flattened and scale-like with the margin relatively near the leaf surface. There is not a marginal palisade of waxy spines.

Pupae: The pupa or fourth nymphal instar will be somewhat darker beigeish-yellow and opaque and 0.6 to 0.8 mm long. Pupae are relatively more plump compared to previous nymphal stages. The apex of anterior and caudal spiracular furrows have smalls amount of white wax deposits. The caudal setae are prominent, and the caudal end is somewhat acute. Dorsal spines are present when the host leaf is hairy and absent when the host leaf is smooth.

BIOLOGY Distribution: Silverleaf whitefly probably occurs around the world in tropical and subtropical areas and in greenhouses in temperate areas. It has been reported from California, Florida and it occurs in North Carolina.

Host Plants: Alfalfa, beans, broccoli, Citrus, Ficus, Lantana, lettuce, melons, cotton, grape, sweet potato, and poinsettia are definite hosts of the silverleaf whitefly. Gerbera daisies are probably hosts.


Damage: Direct damage is caused by the removal of sap, and indirect damage as a disease vector. The silverleaf whitefly is a vector for several important virus diseases of lettuce and melons in the southwestern United States. Both the adult and nymphal stages contribute to direct damage. Chlorotic spots sometimes appear at the feeding sites on leaves, and heavy infestations cause leaves of cucurbits and stems of poinsettias to blanch (“silver”) and wilt. The excretion of honeydew and the subsequent development of sooty mold fungi also reduces the appearance, photosynthesis, and other physiological functions of the plant. Even though the silverleaf whitefly is considered an economic pest, economic thresholds have not been generated for this pest on ornamental plants.

Life Cycle: (The following information was observed with whiteflies that were undoubtedly silverleaf whiteflies although at the time they were thought to be sweetpotato whiteflies.) Developmental times from egg deposition to adult emergence appears to be primarily controlled by temperature, humidity, and host plant. These times will vary from 16 to 38 days depending on these factors. The number of eggs laid by each female over her lifetime varies considerably, but appears to be around 80 to 100. There have been reports (in Israel) that repeated applications of insecticides have produced a 9 highly fecund (300 eggs/females) strain of silverleaf whitefly. Apparently, at temperatures above 36°C eggs fail to hatch. “Crawlers” hatch from the eggs and crawl about until they insert threadlike mouthparts into the underside of the leaf to feed. They tuck their legs and antennae underneath and settle down closely to the leaf surface.

Crawlers molt into scale like nymphs that also suck out sap. Nymphs molt a second and third time. The fourth stage eventually becomes a non-feeding pupa. The adult whitefly develops within the pupa. Adults emerge from the pupa through a T-shaped slit about a month from the time the egg was laid. Females live about two weeks.

CONTROL Control of silverleaf whiteflies is difficult because the eggs and older immature forms are resistant to many aerosol and insecticide sprays (in addition, the adults are extremely resistant to dry pesticide residue). For good control, the pesticide mixture must be directed to the lower leaf surface where all stages of the whiteflies naturally occur. One must make regular applications of pesticides to control crawlers and second stage nymphs until the last of a whole generation of immature whiteflies has hatched. However, some of the pyrethroid pesticides are somewhat more effective and need not be applied as often. Neem seed extract is not as acutely toxic as some of the synthetic pesticides, but has the advantage of being toxic to young nymphs, inhibiting growth and development of older nymphs, and reducing oviposition by adults.

Bandedwinged Whitefly

DESCRIPTION Adults: Mature adult bandedwinged whiteflies have zig-zag bands across the front pair of wings. The hind pair of wings are unmarked. With the exception of the front banded wings this whitefly is very similar to greenhouse whitefly.

Eggs: The eggs are about 0.12 mm long and 0.10 mm wide. Eggs are placed randomly or in circles on the leaf underside. Newly deposited eggs are pale yellow and turn pale pinkish just before hatching.

Nymphs: Young nymphs are 0.37 mm long, and as nymphal stages progress become just over one-half mm long. They are translucent white, with a yellow spot on each side of the abdomen. When the first instar nymph first settles down it begins to secrete a wax fringe that will become the side walls of the pupal case. As growth occurs the nymphal stages will secrete a marginal fringe of translucent setae, and the dorsal medial area of the integument becomes brown.

Pupae: The pupal case is just short of 1 mm long and 0.5 mm wide. The translucent marginal setae are of two lengths and the marginal palisade of wax rods is very distinct. The dorsal medial region is dark brown and uneven; the operculum is yellowish brown.

BIOLOGY Distribution: Arizona, California, Colorado, District of Columbia, Florida, Georgia, Illinois, Indiana, Kansas, Kentucky, Louisiana, Maryland, Mississippi, Missouri, New Mexico, New York, North Carolina, Pennsylvania, South Carolina, Texas, Utah, and Virginia. In northern areas this whitefly probably survives the winter only in greenhouses, but in warmer areas lives outdoors on weed hosts.

Host Plants: Originally described on Abutilon theophrasti, but is now considered a polyphagous feeder. Some common weed hosts are Ambrosia, Bidens, and Sida. Some important ornamental hosts include Euphorbia (poinsettia), Geranium, Hibiscus, and Petunia.

Damage: Infested plants become chlorotic and unthrifty from sap removal. Honeydew and sooty mold also detract from the aesthetics of the crop. Unless controlled, bandedwinged whitefly can be very damaging to a floriculture crop.

Life Cycle: Bandedwinged whitefly reproduces much like the more studied greenhouse whitefly. Temperatures will greatly affect the time required for a complete generation. It is known that eggs will hatch in about 12 days at early April temperatures of a Kentucky greenhouse.

CONTROL Controls after establishment of major infestations will be very similar for all whiteflies in a situation. Prevention of greenhouse invasion from out-of-doors in the fall will make controls much easier in late fall to early winter. Part of this prevention will have to involve sanitation with respect to weed hosts around the greenhouse, both indoors and outdoors. Also, the proper disposal of rejected and remaining infested plants in the fall is important.

Chemical controls will be similar regimens for nearly all whiteflies. Biological controls would perhaps be an important alternative on perimeter plants, and on plants that have a longer growing season.

Sweet Potato Whitefly

DESCRIPTION Adults: Adult sweetpotato whiteflies are small, approximately 1/25 inch in length, with a pale yellow body and two pairs of white wings and covered with a white waxy powder. At rest, wings are held in an inverted V position. Their compound eyes are red.

Eggs: Female whiteflies deposit pear-shaped eggs into the mesophyll or inner tissue of the leaf from the lower surface. Eggs are attached to the leaf by a stalk-like process. Eggs are white when first laid, and become brown prior to hatching. They are generally laid on the underside surface of the younger, upper leaves of the plant.

Nymphs: The first nymphal stage is called crawlers and the last stage is often referred to as the pupa. After hatching the crawlers move a short distance and settle to feed. Once settled, the subsequent three nymphal stages are scale-like and sedentary. Nymphs are creamy white to light green and oval in outline. The total nymphal period lasts about 2-4 weeks.

Pupae: The pupa or fourth nymphal instar will be somewhat darker beigeish-yellow and opaque and 0.6 to 0.8 mm long. Pupae are relatively more plump compared to previous nymphal stages. The apex of anterior and caudal spiracular furrows have smalls amount of white wax deposits. The caudal setae are prominent, and the caudal end is somewhat acute. Dorsal spines are present when the host leaf is hairy and absent when the host leaf is smooth.

BIOLOGY Distribution: In addition to Hawaii, the sweetpotato whitefly has been reported as a serious pest of cultivated crops in tropical and subtropical areas including Africa, Asia, Central America, South America, and the West Indies where it is also known as the tobacco whitefly and cotton whitefly. In North America, it has been reported from Arizona, California, District of Columbia, Florida, Georgia, Maryland, Texas and Mexico (Cock, 1986).

Host Plants: The sweetpotato whitefly has an extremely wide host range. It attacks more than 500 species of plants (Greathead, 1986) from 63 plant families (Mound and Halsey, 1978). In Hawaii, the sweetpotato whitefly has been found on the following crop plants: annona (cherimoya, atemoya, sugarapple), avocado, broccoli, cauliflower, Chinese cabbage, Chinese waxgourd, cucumber, Dendrobium (flowers), edible gourds,
eggplant, fig, green bean, guava, hibiscus, hyotan, lettuce, luffa, plumeria, poinsettia, pumpkin, rose, soy bean, squash, sweetpotato, togan, tomato, ung-choi, watermelon, yardlong beans and zucchini. Although not yet reported in the state, other crop hosts include cabbage, chrysanthemum, beans, bittermelon, dishrag squash, pepper, pea, and radish (Mau & Tsuda). Weeds often serve as alternate hosts of crop pests.

Damage: Direct feeding damage is caused by the piercing and sucking sap from the foliage of plants. This feeding causes weakening and early wilting of the plant and reduces the plant growth rate and yield (Berlinger, 1986). It may also cause leaf chlorosis, leaf withering, premature dropping of leaves and plant death. Infestations of sweetpotato whitefly nymphs are associated with the occurrence of irregular ripening of tomatoes and silverleaf of squash. Indirect damage results by the accumulation of honeydew produced by the whiteflies. This honeydew serves as a substrate for the growth of black sooty mold on leaves and fruit. The mold reduces photosynthesis and lessens the market value of the plant or yields it unmarketable (Berlinger, 1986).

Damage is also caused when sweet potato whitefly vectors plant viruses. A small population of whiteflies is sufficient to cause considerable damage (Cohen and Berlinger, 1986). Plant viruses transmitted by whiteflies cause over 40 diseases of vegetable and fiber crops worldwide. Among the 1,100 recognized species of whiteflies in the world, only three are recognized as vectors of plant viruses. The sweetpotato whitefly is considered the most common and important whitefly vector of plant viruses worldwide. It is also the only known whitefly vector of viruses categorized in the geminivirus group.

Life Cycle: Whiteflies have six life stages – the egg, four nymphal stages, and the adult. The development time of this insect from egg to adult may range from 15-70 days dependent upon temperature and plant host. Development occurs in temperatures ranging from 50 to 89.6°F (10 to 32°C). 80.6°F (27°C) appears to be the optimal temperature for development. Under control conditions on cotton, the pest completes its development in 17 days at 86°F (30°C) On the contentinal U.S. development from egg to adult under field conditions varies with the season; development varies from 25 to 50 days.

Adults usually emerge from their pupal cases in the morning hours and may copulate a few hours later. Oviposition occurs from 1 to 8 days after mating. Adult life span ranges from 6-55 days dependent on temperature. Females live only 10-15 days under southern continental U.S. summer conditions, but can live several months during the winter. In this species, reproduction can occur with or without copulation. Unmated females can reproduce by parthenogenesis in which the females produce only male progeny. Females lay 80 to more than 300 eggs in their lifetime. The plant host reportedly plays an important role in female fecundity.

CONTROL High reproductive rate and multiple host sequences provide optimal conditions for sweetpotato whitefly population development. The varied habitats, seasonal population development and intra and inter-crop and wild host movement present an extremely complex and difficult challenge requiring new and innovative approached for formulating control and suppression methodology.

There is really no easy way of controlling the sweetpotato whitefly. Egg mortality is usually minimal. Weather and predation may cause high mortality rates during the crawler and first nymphal stages, but has only moderate effects on the later nymphal stages. In the past adults were easily killed with insecticides but pesticide resistance in sweetpotato whitefly populations is a common problem faced by many growers today. Sweetpotato whitefly has become resistant to chemical insecticides quite rapidly in other parts of the world, and the wisdom of relying only on chemical insecticides is questioned. Moreover, regular insecticide applications can result in resurgence of other pests.

We believe that a combination of cultural practices and chemical application would provide the best chance of controlling this pest. The use of sound cultural practices that may avoid, delay, or lessen the severity of the sweetpotato whitefly infestation is a good foundation to begin with. Careful selection of insecticides can help regulate sweetpotato whitefly populations to reduce losses not due to pathogenic organisms. Little can be done to reduce losses due to virus diseases, but we are fortunate that none have been introduced

Azalea Whitefly

DESCRIPTION Adults: About 1.5 mm long, the adult is light yellow with the antennae and legs slightly
lighter in color. Most of the body is covered with a white, waxy bloom. The eyes appear dark brown.
As usual, the small moth-like adults fly about readily when infested plants are disturbed.

Eggs: Azalea whitefly eggs are typical of other whiteflies in their irregular cylindrical shape that
is somewhat pointed at one end and rounded at the other (base end). The base end has a tiny protuberance
that is inserted into the leaf tissue. The eggs are 0.1 mm wide and 0.22 mm long. Color ranges from
translucent creamy to dark gray tipped fading to paler gray at the base.

Nymphs: The tiny nymphs, are oval and light in color without any form of wax secretions.

Pupae: The pupal case is light yellow to an orange yellow in color, without any form of wax secretions
and about 0.84 mm long. The marginal areas appear lighter in color than the mid-dorsal area. Some
marginal indentations may be present when the pupal case has grown against the leaf hairs.
BIOLOGY Distribution: This whitefly has been spread worldwide wherever azaleas grow. The first records
in the United States were on plants received from Holland in 1910. Without a doubt azalea whiteflies
occur in all southeastern states.

Host Plants: Azalea whiteflies infest all species of azaleas.

Damage: Infested plants become unthrifty, honeydew, and sooty mold detract from a healthy appearance.
Unless controlled, large clouds of whiteflies take to the air when heavily infested plants are disturbed.

Life Cycle: Little is known about this whitefly and its life cycle. Presumably it is very similar to
other whitefly species. This whitefly overwinters as nymphs on azalea leaves. Adults emerge in early
spring in North Carolina and lay eggs on the undersides of azalea leaves. The eggs are creamy and
translucent, but turn gray as they age.

« Previous Page — Next Page »

Copyright © 2008 Hydroponics Dictionary. All Rights Reserved - Website Design by Audiobloc. Site search engine optimisation by search engine optimisation Sitemap